Clamshell bucket



l 6, 1943- D. M. SCHWARTZ 2,315,985

CLAMSHELL BUCKET 4 Sheets-Sheet 1 Filed Oct. 19, 1942 April 1943- D. M. SCHWARTZ 2,315,985 CLAMSHELL: BUCKET Filed Oct. 19. 1942 4 Sh eets-Sh eet 3 April 6, 1943.

D. M. SCHWARTZ 2,315,985

CLAMSHELL BUCKET Filed Oct. 19, 1942' 4-Sheets-Sheet 4 5'wmMMW?{ii a fun-ml. B

INVENTOR Patented Apr. 6, 1943 CLAMSHELL BUCKET Daniel M. Schwartz, Pittsburgh, Pa., assignor to Dravo Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application October 19, 1942, Serial No. 462,486

6 Claims.

This invention relates to clamshell buckets. In Letters Patent of the United States, No. 1,968,498, granted July 31, 1934, on the application of Bernard H, Kersting, apparatus is shown and described for operating clamshell buckets. The apparatus of the patent named includes means for equalizing the stresses to which the holding line and the closing line are subjected. The present invention is found in improvement in such equalizing means, whereby accuracy and durability are enhanced.

In the accompanying drawings Fig. I is a view in side elevation of a clamshell bucket as it hangs suspended, in organization with operating apparatus; Fig. II is a diagrammatic view, showing,

analyzed out from Fig. I, the sheaves and the lines reeved upon them; Fig. III is a view to smaller scale, showing a loading tower for coal or other such material, the tower being equipped with a clamshell bucket and operating apparatus that embodies the invention; Fig. IV is a diagrammatic view, showing the bucket-operating apparatus, analyzed out from Fig. III; Fig. V is a view, comparable in scale to Fig. I, and showing in elevation a fragment of the operating apparatus of Fig. III; Figs, VI and VII are views to yet larger scale, showing in end elevation and in longitudinal and horizontal section one of the elements which in Fig. V appears in organized assembly; Figs. VIII and IX are views that, corresponding to Figs. V and VII, illustrate a modification; Fig. X is a view that corresponds to Fig. IX, and illustrates a variation in structural detail.

The bucket shown in Fig. I consists of or includes two complementary jaws J with extensions E by which they are pivoted in a housing H. Through toggle links L the jaws are pivoted to a block B. The block B carries a sheave 2, and sheave 2 rests in a bight in the holding line 3. Mounted upon a common axle with sheave 2 are other sheaves 260, and mounted upon an axle secured in housing H are sheaves 6. Over sheaves 280 and 6 is trained the closing line 1. The sheaves 200, so organized, constitute the standing block, and the sheaves 6 the running block of tackle. As the holding line 3 is paid out and taken in, the bucket is lowered and raised; as the closing line is taken in, the jaws close to the full-line position; as the closing line is paid out, the jaws of the bucket swing under gravity to the open position, shown in broken lines in Fig. I. The two .jaws of the bucket are provided on the axes of their pivotal mounting in housing H with gears which by their intermeshing insure equality in the simultaneous turning of the jaws.

Referring to Fig. III, a tower 30 is shown that carries a boom 29. Theboom extends horizontally and is carried at a suitable height above the ground on which the-tower is erected. Upon suitable tracks that extend through the length of the boom a carriage I4 is mounted to travel. Beyond the ends of the range of carriage travel sheaves 24 and 25 are rotatably mounted upon the boom. A drum 23 is mounted in the boom and is subject to suitable driving power. Upon drum 23 rack line 22 is wrapped, and from the drum the rack line extends, trained over sheaves 24 and 25, and is secured at its ends to carriage M (of. Fig. IV), Manifestly, as drum 23 is rotated in one direction and the other, the carriage I4 is shifted upon its tracks, longitudinally of the boom.

The bucket is hung from the carriage, and in Figs. III and IV the letter B serves generally to designate the bucket. Sheaves l5, IS, IT, and I8 are rotatably mounted in carriage I4. Beyond the range of carriage travel sheaves i9, 20, and 2| are rotatably mounted upon the boom: sheaves I9 and 2| at one end, sheave 20, at the other. Drums 5 and 8 are mounted in the boom, and are subject to suitable driving power. Upon drum 5 both the holding line 3 and the closing line l are, each at one end, anchored and wrapped; upon the drum 8 the closing line I at its opposite end is anchored and wrapped. From the bucketsustaining bight (of. Figs. II and IV) the holding line 3 extends, on the one hand, over sheave |5 to an anchorage 4 (to the left, Fig. IV), and, on the other, over sheaves I1 and I9 to the drum 5, From the tackle that includes the standing block 200, 200 and the running block 6, 6, 6, the closing line '1 extends, on the one hand, over sheaves l6 and 20, to drum 8, and,,on the other, over sheaves I8 and 2|, to drum 5. By the turning of drum 5 the bucket is raised and lowered; by the turning of drum 8 the bucket is opened and closed. 7

A counterweight 2B is sustained in a bight in a line 21. Line 21, anchored at one end, is at its opposite end wrapped upon and secured to drum 5. The wrapping is in opposite direction to that of lines 3 and I upon the same drum. The counterweight, so arranged, is effective to relieve thel hoisting engine that drives drum 5 of torque due to the weight of the bucket.

In apparatus so constructed and organized provision should be made, that inequalities due to unequal stretching of the holding and closing that, as lever 5| swings, the holding and closin lines will in effective length be accommodated to one another, that both always may be taut; From" one arm of the lever, and advantageously the lower arm (Fig. V), the arm in which the anchorage 4 is set, a stem 52 extends. This stem conveniently extends in substantial alignment with the adjacent reach of the holding line 3, and may be regarded as in some sense an inflexible prolongation of the holding line beyond the point of anchorage 4. The anchorage 4 takes the form of a block pivoted in the lowerarm, and from this block'also the stem 52 extends. As the lever swings, the stem 52 is reciprocated longitudinally. The longitudinal shifting of the stem 52 is springbacked in both directions. Upon stem 52, be tween follower plates 55 and 56, are set springs 51. The follower plates, movable toward one another upon stem 52, are held against separation beyond an interval defined by and between adjustable nuts 53 and 54. This assembly of stem and springs is enclosed in a housing 58, and within the housing abutments 5D and 6| are set. Slight angular movement of stem 52 in vertical plane finds compensation in the pivotal mounting of housing 58 in the boom structure, as indicated at 62. Referring particularly to Figs. V and VII, it will be seen that within a narrow range the swing of lever 5| is free, and that, beyond such range, further swing is cushioned, and is opposed by a mounting resistance of substantial magnitude.

Manifestly, small inequalities due to unequal stretching of the holding and closing lines find compensation in the swing of lever 5| within its range of free turning. And this range is by the movement of nuts 53 and 54 adjustable, both initially and from time to time. The apparatus has sheave Zlll is carried (the sheave over which the closing line is trained). Upon the opposite, left-hand end of stem 520 a sheave 63 is mounted, and over sheave 63 the holding line 3 is trained, and from the sheave 63 the holding line extends to its anchorage 4, fixed in the boom structure.

Whereas, in the structure of Figs. VIII and IX, the nuts 53 and 54 bear immediately upon the follower plates 55 and 56, between which the springs 51 are compressed, in the modified structure of Fig. X, the follower plates bear immediately upon the abutments 60 and 5 with the nuts 53 and 54 spaced from the plates, as shown in the drawings. The range of free movement; of the spring-equipped stem, which is in the structure of. Fig. IX afiorded by the provision of clearances between the follower plates 55, 56 and the abutments 60, BI, is in the modified structure of Fig. X gained by spacing the nuts 53 and 54 from the follower plates.

Manifestly, in each of the tructures described, the same compensating effect for unequal line stretch is afforded; and the same accumulation of spring tension to complete bucket closure is afforded.

' bucket that includes bucket, holding line, and

additional value and advantage in its capability of bringing the bucket to closed position and holding it securely closed, and preventing spilling. When by the rotation of drum 8 the bucket is being closed, the tension upon the closing line I,

exerted through sheave 20l, swings the lever 5| clockwise (Fig. V), drives stem 52 to the left, and puts springs 51 under compression. The operator starts the hoisting engine and sets drum 5 in rotation (counter-clockwise, Fig. IV) just before bucket closing is completed. This relieves T some of the tension upon th closing line and allows the springs 51 to become effective in completing the closing of the bucket. The limit switch associated with the drive for drum 8 is so set that drum 8 stops while the bucket is still a few inches ends of housing 58 (which may be similarly mounted in the structure of boom 29) Interiorly of the housing the spring arrangement is the 7 same as that already described. Upon one end of stem 520 (the right-hand end, Fig. VIII) the closing line, the invention herein described, which consists in an equalizer and cushion device, such device consisting of a longitudinally reciprocable stem, means for effecting reciprocation of the stem in one direction or the other in response to the tension upon one or other of the said lines in excess of that upon the companion line, the said stem so subject to opposed tensions being freely reciprocable within a limited range, and spring resistance to stem reciprocation through wider range.

3. In apparatus for operating a clamshell bucket that includes an elongate boom, a carriage traveling upon the boom, a bucket hung from the carriage, and holding and closing lines mounted in the boom and engaging the bucket, the invention herein described, which consists in an equalizer and cushion device, such device including a beam pivoted medially upon a fulcrum fixed in the boom, one arm of the beam being equipped with a sheave over which the closing line is trained, and the other arm of the beam afiording anchorage for the holding line, and spring resistance to the swinging of the beam in either direction.

4. In apparatus for operating a clamshell bucket that includes an elongate boom, a carriage traveling upon the boom, a bucket hung from the carriage, and holding and closing lines mounted in the boom and engaging the bucket, the invention herein described, which consists in an equalizer and cushion device, such device including a beam pivoted medially upon a fulcrum fixed in the boom, one arm of the beam being equipped with a sheave over which the closing line is trained, and the other arm of the beam afiording anchorage [or the holding line, a stem reciprocable in the plane of the swing of the beam and in a line transverse to the longitudinal extent of the beam, such stem being engaged by the beam at a point remote from the fulcrum of the beam, and spring resistance to stem reciprocation in either direction.

5. In apparatus for operating a clamshell bucket that includes an elongate boom supported in elevated and horizontally extending position, a carriage traveling upon the boom, a bucket hung from the carriage, and holding and closing lines mounted on the boom and engaging the bucket, the invention herein described, which consists in an equalizer and cushioning device, such device including a housing pivotally mounted in the boom structure, a stem extending longitudinally through the housing, the said holding and closing lines having connection with said stem, and the said stem being responsive in longitudinal reciprocation to inequalities of tension exerted upon the said holding and closing lines and by its reciprocation relieving such inequalities of tension, and spring resistance to stem reciprocation simultaneously engaging such housing and stem.

6. In apparatus for operating a clamshell bucket that includes an elongate boom supported in elevated and horizontally extending position, a carriage traveling upon the boom, a bucket hung from the carriage, and holding and closing lines mounted on the boom and engaging the bucket, the invention herein described, which consists in an equalizer and cushioning device, such device including a beam pivotally mounted in the boom structure and adapted to swing in vertical plane, such beam carrying an idly mounted sheave and a pivotally mounted block, the closing line being trained upon the said sheave and the holding line being anchored in said block, a stem extending from said block in the plane of the swing of the beam and in a line transverse to the longitudinal extent of the beam, and spring resistance to stem reciprocation in either direction.

DANIEL M. SCHWARTZ. 

